This question already has an answer here:
The valkyries are female demigod warriors from the Norse mythology. They served Odin by choosing, among the warriors in a battle, who dies and who lives and from the ones who die which ones go to Valhalla, to become Odin's einherjar and wait in the Valhalla's hall for Ragnarok.
Is it explained how do the valkyries choose among this warriors either who dies or which dead warriors go to Valhalla? For example, based on certain traits like courage or skill in battle.